First Paris St-Germain threatened to make second leg of the Champions League knock-out tie with Valencia a foregone conclusion, then, as is their custom, they made it intriguing for neutrals by making it complicated for themselves. When Carlo Ancelotti's team raced into a 2-0 lead at the Mestalla three weeks ago it looked as if the home leg would be a breeze. Now, with Valencia due at the Parc des Princes and PSG wobbling, they risk suffering a big blow.

PSG were superb for most of the away leg, with Ezequiel Lavezzi and Javier Pastore scoring to reward a performance of wonderful verve and vigour while the home goalkeeper, Vicente Guaita, excelled to prevent the visitors from inflicting further damage. However, in the last minute of that game they allowed the Valencia centre-back Adil Rami to head a goal for the Spaniards and, moments later, Zlatan Ibrahimovic lunged at Andrés Guardado to get himself sent off and suspended for the return leg. The Swede's absence gives Ancelotti the biggest of several selection puzzles ahead of a match that has also been made more difficult by a dip in domestic form and a controversial public pronouncement by Leonardo, the club's sporting director.

A short time ago PSG were basking in the glow of signing David Beckham and opening up a seemingly unassailable lead at the top of Ligue 1, but the late slackness at Valencia spilled over into their domestic form, where PSG lost their next game 3-2 to lowly Sochaux and on Saturday they suffered another surprising reverse, becoming the first side in nearly five months to lose at Reims. That prompted Leonardo to complain about "conditions" and declare that PSG's team is "based on talent and quality of passes" and thus "made to play in Europe rather than the [French] league".

That comment was interpreted as an arrogant put-down of the rest of France, meaning Leonardo committed the double offence of, firstly, spouting the sort of snootiness that the club's image-conscious Qatari owners have tried to avoid since taking over in 2011 and, secondly, seeming ungrateful for the hundreds of millions of euros that his employers have invested in that time.

Leonardo's position has been precarious for a while and, according to Le Parisien newspaper, the owners are "surprised and disturbed" by his latest assertion. Ancelotti's job is also in jeopardy. A recurrence of the team's inconsistency in Ligue 1 is a reminder of his failure to win the title last season. Ibrahimovic, the team's top scorer and talisman, is irreplaceable, but Ancelotti has hinted that the France international Kevin Gameiro will be entrusted with the task of impersonating him against Valencia.

It remains to be seen, meanwhile, who will replace Marco Verratti in midfield, the dynamic 20-year-old having got himself suspended with a yellow card in the first leg. Beckham is one option, even though he made little impact after replacing the Italian in the 60th minute of the defeat at Reims, and Thiago Motta is another, although he is short of match fitness having missed nearly two months through injury. This means Clément Chantôme could start.

One certain starter is the Brazil centre-back Thiago Silva, who will make his long-awaited return to the side after a two-month injury layoff. Ancelotti must decide whether to drop Alex or Mamadou Sakho to accommodate the returning captain and that decision has been made more difficult by the fact that recent displays have given the manager reason to want to drop both.

There is also the question of how Ancelotti will approach the match knowing that his side are in front. The fact that Valencia have problems in defence too, with Rami and Ricardo Costa injured, could incite Ancelotti to be bold – at the risk of allowing the visitors to hit them on the counterattack. "We have to forget about the first leg," says Ancelotti. "We have to try to play our football and defend well and attack well. That's our goal."